A. ACIS T_GAIN Epoch 50

The periodic ACIS T_GAIN correction upgrade for May - Jul 2012 has
been released. The corrections are at nominal/expected levels of less
than 2% of the energy value. This upgrade as usual affects
observation data taken over Epoch 50 and 49, and so would update PHAs
for OBS_IDs taken since 01 February 2012. Users with such datasets
are encouraged to revalidate their analysis results after
reprocessing their data with the upgraded CalDB files. For specific
details of the new calibrations in this release, see the technical details section below.

Please Note: As of 10/04/2012we have been
informed that the
above ACIS BKGRND files version N0002 have yet another problem
resulting from their being rebuilt. The error causes the files to be
useless and also causes acis_bkgrnd_lookup to fail. I apologize for
the inconvenience! We are working to replace the files within about
one week.

We have found that the ACIS "Group E" blank-sky BKGRND files
(those that become effective on 2005-09-01T00:00:00) have an error in
their headers that produces a bad coordinate transform column
"pha_COORD" in dmcopy and reproject_events, which in turn causes
scripts such as specextract to
fail. For further information, see the technical details section below.

PIPELINES/TOOLS AFFECTED:

THREADS AFFECTED:

III. TECHNICAL DETAILS

A. ACIS T_GAIN Epoch 50

The ACIS time-dependent gain corrections (T_GAIN) have recently
been updated for current changes from the previous T_GAIN epoch,
specifically Epoch 50, which was May through July 2012. With
the addition of these new corrections, derived from ACIS External Cal
Source (ECS) data taken during radiation zone passes, the CalDB files
extending from Feb 01 2012 through May 2012 (i.e. Epoch 49) have been
finalized, and new non-interpolating T_GAIN files are now implemented
for Epoch 50.

The magnitudes (in eV) of the new gain corrections, versus photon
energy, are given in Figs. 1-3 below. The corrections are of the
usual order in magnitude, specifically less than 2.0% of the photon
energy value. Fig. 1 below gives the corrections for the ACIS-I
aimpoint on chip ACIS-3, for the CTI-corrected case, which is the
only one applicable to FI chips. Figure 2 gives the corrections for
the ACIS-S aimpoint on ACIS-7, for the case where the BI chips are
CTI-corrected. Finally Fig. 3 gives the corrections for ACIS-7 for
NON-CTI-corrected BI chips. These would be relevant to GRADED
DATAMODE observations with ACIS-S, for example.

B. ACIS Group E BKGRND Version 2

The lastest set of ACIS Blank-sky Background files, labeled
collectively as "GROUP E", which also have effective date 2005-09-01,
have been found to have two errant structural keywords in their
headers. Specifically the header keys "LATP9" and "EQUI9" are
present, which causes an inappropriate coordinate transform column to
appear in those files. Other BKGRND files don't have these
keywords.

The bad coordinate transform column appears as follows when
dmlist-ing the columns of the BKGRND files:

6: pha_COORD = pha

Users have found that the script specextract fails when these
GROUP E BKGRND files are used in the blank-sky background file
thread, to reproject the events there-in and allow background level
estimates for extended source analyses.

We have corrected this problem by rebuilding these BKGRND files
with the above two keywords removed from the headers. All 18 of the
files have been corrected this way, and their version numbers have
been upgraded to N0002, so that they will not be confused with the
errant files.

Matching CIAO and CALDB Versions

News

CalDB 4.7.2,
an upgrade to CalDB 4.7.0 and later versions, has been released. Included are two items which affect only
ACIS GRADED CC-mode Obs_IDs taken since 2009-11-01: 1) ACIS GRADE file N0005, previously released with CalDB 4.6.4,
has been retracted, and 2) the special ACIS QE for CC-modes has been re-indexed so that it will be used for all
GRADED CC-mode observations over the full life of the mission.
See the CALDB 4.7.2 Release Notes for details.

25 Mar 2016

CalDB 4.7.1,
an upgrade to CalDB 4.7.0 and later versions, has been released. Included are the quarterly ACIS T_GAIN
upgrades for Epochs 63 (Aug-Oct 2015) and 64 (Nov 2015 - Jan 2016). Provisional and upstaged ACIS T_GAIN
files from 2013 and 2014 have been deleted from the distribution and index.
See the CALDB 4.7.1 Release Notes for details.

15 Dec 2015

CalDB 4.7.0,
an upgrade to CalDB 4.6.5 and later versions, has been released. Included are the quarterly ACIS T_GAIN
upgrades for Epochs 62 (May-Jul 2015) and 63 (Aug-Oct 2015), a modified ACIS QE for older CC-mode observations,
annual updates to the HRC-I Gain Map and PI background spectrum files, and two new HRC-I BKGRND event lists for
2014 and 2015, respectively. See the CALDB 4.7.0
Release Notes for details.

CalDB 4.6.9
an upgrade to CalDB 4.6.5 and later versions, has been released. Included are the quarterly ACIS T_GAIN
upgrades for Epochs 61 (Feb-Apr 2015) and 62 (May-Jul 2015), an improved gain table for ACIS-S1, and new
LSF parameter files for the LETG/HRC-S configuration, with modified mean QE's for HRC-S and HRC-I.
See the CalDB 4.6.9
Release Notes for details.

01 Jul 2015

CalDB 4.6.8,
an upgrade to CalDB 4.6.5 and later versions, has been released. Included are the quarterly ACIS T_GAIN
upgrades for Epoch 60 (Nov-Jan 2015) and 61 (Feb-Apr 2015), as well as "revision A" files for Epochs 56
through 59 which have minor corrections.
See the CalDB 4.6.8 Release Notes for details.